Home > Articles

Programming with .NET

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Visual Basic .NET

Visual Basic .NET is the next revision of the popular Visual Basic programming language, which has roots in the BASIC programming language itself. Known for its rapid application development capability, Visual Basic .NET provides developers with the benefits of rapid development with a full-blown object-oriented (OO) programming language. Visual Basic .NET builds on the basic OO features present in Visual Basic and makes the object- orientedness of the language on par with that of Visual C# and even C++.

With its human-readable code syntax, Visual Basic .NET follows a task-oriented model. Focus on increased developer productivity still remains the core mantra for Visual Basic. Key features of the Visual Basic .NET programming language include the following:

  • A full, object-oriented, yet intuitive, programming language

  • Typical VB features such as implicit typing, late binding, default variable initialization, and optional parameters

  • Enhanced event handling

  • Parameterized properties

  • -Redeclaration of interface members on implementation

  • Command-line/SDK compilers

Hello World

The program listing that follows will look both familiar and different to existing Visual Basic programmers. Familiar is the overall style, subroutines, and modules. What is different in the program is really the additional keyword—Namespace—and the use of -the .NET Framework class library. An important thing to keep in mind is that Visual Basic .NET not a case-sensitive programming language.

Imports System
Namespace hks
  Module HelloWorld
    Public Sub Main()
      Console.WriteLine("Hello World in VB")
    End Sub
  End Module
End Namespace

Visual Basic .NET programs are stored with the .vb extension. To compile a Visual Basic .NET program, use the Visual Basic. NET J# command-line compiler, vbc.exe.

vbc HelloWorld.vb

Leverage Your VB Skills with Visual Basic .NET

A key highlight of the Visual Basic .NET programming language is that it allows developers to utilize their existing skills in Visual Basic development. Apart from skills reuse, Visual Basic .NET supports importing existing Visual Basic projects for migration.

Comments

Visual Basic comments are plain old ' style line comments or are identified by Rem.

Imports System
Namespace hks
  Module Comments
    Rem Implement the Main Method
    Public Sub Main()
      ' Print Out Hello World
      Console.WriteLine("Hello World in VB")
    End Sub
  End Module
End Namespace

Data Types

Table 3.2 describes how the Visual Basic .NET types are mapped to their corresponding .NET Framework types.

Table 3.2 Visual Basic .NET Data Types

Visual Basic .NET Type

Corresponding .NET Framework Type

Boolean

System.Boolean

Byte

System.Byte

Char

System.Char

Decimal, Double, Single

System.Decimal, System.Double, System.Single

Short, Integer, Long

System.Int16, System.Int32, System.Int64

Object

System.Object

String

System.String


Enumerations

Enumerations are supported in Visual Basic .NET. Listing 3.6 illustrates a potential use.

Listing 3.6 Using Enumerations (Visual Basic .NET)

Imports System
Namespace hks
  Module UseEnumerations
    Public Enum CreditCard
      Visa
      MasterCard
      AmericanExpress
      Discover
    End Enum
    Public Sub Main()
      Dim cc as CreditCard
      cc = CreditCard.Visa
      Console.WriteLine(cc)
    End Sub
  End Module
End Namespace

Arrays

Arrays, which are subclasses of the System.Array type, are supported in Visual Basic .NET (Listing 3.7).

Listing 3.7 Using Arrays (Visual Basic .NET)

Imports System
Namespace hks
  Module UseArrays
    Public Sub Main()
      Dim days_of_week() as String = { _
        "Sunday", _
        "Monday", _
        "Tuesday", _
        "Wednesday", _
        "Thursday", _
        "Friday", _
        "Saturday" _
      }
      Dim I as Integer
      For I = 0 to days_of_week.Length-1
        Console.WriteLine(days_of_week(I))
      Next I
    End Sub
  End Module
End Namespace

Variables and Constants

Using variables is similar to the traditional Visual Basic programming, using the Dim keyword (see Listing 3.8).

Listing 3.8 Using Enumerations (Visual Basic .NET

Imports System)
Namespace hks
  Module UseVariables
    Public Sub Main()
      Const HELLO_WORLD as String = "Hello World"
      Dim msg as String = HELLO_WORLD & " in VB"
      Dim mc as New MClass(msg)
      Call mc.Print
    End Sub
  End Module
  Class MClass
    private message as String
    Public Sub New(ByVal message as String)
      Me.message = message
    End Sub
    Public Sub Print()
      Console.WriteLine(message)
    End Sub
  End Class
End Namespace

Expressions

Expressions provide the capability to computerize and manipulate data.

Imports System
Namespace hks
  Module UseExpressions
    Public Sub Main()
      Dim a as Integer = 10
      Dim b as Integer = 10
      Dim result as Integer = a * b
      Dim check as Boolean = (a = b)
      Console.WriteLine(result)
      Console.WriteLine(check)
    End Sub
  End Module
End Namespace

Statements

Statements provide the necessary programming language procedural constructs.

Imports System
Namespace hks
  Module UseStatements
    Public Sub Main()
      Dim msg() as String = {"Hello","World","in","Visual Basic.NET"}
      Dim i as Integer
      For i = 0 to (msg.Length-1)
        Console.Write(msg(i))
      Next
      Console.WriteLine("")
      Dim a as Integer = 10
      Dim b as Integer = 20
      If (a<b) Then
        Console.WriteLine("a<b")
      Else
        Console.WriteLine("a>=b")
      End If
    End Sub
  End Module
End Namespace

Structures

Structures can be used for basic encapsulation of data.

Imports System
Namespace hks
  Module UseStructures
    Public Sub Main()
      Dim hs as New Person("Hitesh","Seth")
      Dim jd as Person = hs
      jd.FirstName = "John"
      jd.LastName = "Doe"
      Console.WriteLine(hs.FirstName & "." & hs.LastName)
      Console.WriteLine(jd.FirstName & "." & jd.LastName)
    End Sub
  End Module
  Structure Person
    Public FirstName, LastName as String
    Public Sub New(ByVal FirstName as String, ByVal LastName as String)
      Me.FirstName = FirstName
      Me.LastName = LastName
    End Sub      
  End Structure
End Namespace

Classes

Classes in Visual Basic are defined using the Class keyword. Like C#, VB classes can have members, constructors and destructors, properties, methods (which are classified into subroutines and functions, depending on whether they return a value), and events (Listing 3.9).

Listing 3.9 Using Classes (Visual Basic .NET)

Imports System
Namespace hks
  Module Useclasses
    Public Sub Main()
      Dim hs as New Person("Hitesh","Seth")
      Dim jd as Person = hs
      jd.FirstName = "John"
      jd.LastName = "Doe"
      Console.WriteLine(hs.FirstName & "." & hs.LastName)
      Console.WriteLine(jd.FirstName & "." & jd.LastName)
    End Sub
  End Module
  Public Class Person
    Private sFirstName, sLastName as String
    Public Property FirstName() as String
      Get
        Return sFirstName
      End Get
      Set(ByVal Value as String)
        sFirstName = Value
      End Set
    End Property
    Public Property LastName() as String
      Get
        Return sLastName
      End Get
      Set(ByVal Value as String)
        sLastName = Value
      End Set
    End Property
    Public Sub New(ByVal FirstName as String, ByVal LastName as String)
      Me.FirstName = FirstName
      Me.LastName = LastName
    End Sub
    Public Function GetFullName() as String
      Return Me.FirstName & "." & Me.LastName
    End Function    
  End Class
End Namespace

Classes can be inherited for overriding and extending functionality present in the base class. The keywords Overridable and Overrides are used to set a method in base class as overridable and implementation of the overridden method in the derived class, respectively (Listing 3.10). Similar to C#, Visual Basic .NET also supports only single inheritance.

Listing 3.10 Using Inheritance (Visual Basic .NET)

Imports System
Namespace hks
  Module HelloWorld
    Public Sub Main()
      Dim hs as New FullPerson("Hitesh","K","Seth")
      Console.WriteLine(hs.GetFullName)
    End Sub
  End Module
  Public Class Person
    Public FirstName, LastName as String
    Public Sub New(ByVal FirstName as String, ByVal LastName as String)
      Me.FirstName = FirstName
      Me.LastName = LastName
    End Sub      
    Public Overridable Function GetFullName() as String
      Return Me.FirstName & "." & Me.LastName
    End Function
  End Class
  Public Class FullPerson
    Inherits Person
    Public MiddleInitial as String
    Public Sub New(ByVal FirstName as String,
ByVal MiddleInitial as String, ByVal LastName as String) MyBase.New(FirstName,LastName) Me.MiddleInitial = MiddleInitial End Sub Public Overrides Function GetFullName() as String Return Me.FirstName & "." & Me.MiddleInitial & "." & Me.LastName End Function End Class End Namespace

Visual Basic .NET supports abstract classes by using the MustInherit and MustOverride keywords (Listing 3.11).

Listing 3.11 Using Abstract Classes (Visual Basic .NET)

Imports System
Namespace hks
  Module UseAbstractClasses
    Public Sub Main()
      Dim hs as New Person("Hitesh","Seth")
      Console.WriteLine(hs.FirstName & "." & hs.LastName)
    End Sub
  End Module
  Public MustInherit Class Abstract
    Public FirstName, LastName as String
    Public Sub New(ByVal FirstName as String, ByVal LastName as String)
      Me.FirstName = FirstName
      Me.LastName = LastName
    End Sub  
    Public MustOverride Function GetFullName as String  
  End Class
  Public Class Person
    Inherits Abstract
    Public Sub New(ByVal FirstName as String, ByVal LastName as String)
      MyBase.New(FirstName,LastName)
    End Sub
    Public Overrides Function GetFullName as String
      GetFullName = FirstName & "." & LastName
    End Function
  End Class
End Namespace

Interfaces

Visual Basic .NET supports interfaces through the Interface keyword. A derived class can implement multiple interfaces and specifies the specific function/subroutine signature implemented through the Interface keyword (Listing 3.12).

Listing 3.12 Using Interfaces (Visual Basic .NET)

Imports System
Namespace hks
  Module UseInterfaces
    Public Sub Main()
      Dim hs as New Person
      hs.Name = "Hitesh Seth"
      hs.Address = "1 Executive Drive, City, NJ 08520"
      Console.WriteLine(hs.GetName())
      Console.WriteLine(hs.GetAddress())
    End Sub
  End Module
  Public Interface IName
    Function GetName() as String    
  End Interface
  Public Interface IAddress
    Function GetAddress() as String    
  End Interface
  Public Class Person
    Implements IName, IAddress
    Private s_name, s_address as String
    Public Sub New()
    End Sub
    Public WriteOnly Property Name() as String
      Set
        s_name = value
      End Set
    End Property
    Public WriteOnly Property Address() as String
      Set
        s_address = value
      End Set
    End Property
    Public Function GetName() as String Implements IName.GetName
      GetName = s_name
    End Function
    Public Function GetAddress() as String Implements IAddress.GetAddress
      GetAddress = s_address
    End Function
  End Class
End Namespace

Exception Handling

New to Visual Basic .NET is structured exception handling, as illustrated in Listing 3.13. Visual Basic typically had the OnError/Goto construct for handling exceptions.

Listing 3.13 Exception Handling (Visual Basic .NET)

Imports System
Namespace hks
  Module UseExceptions
    Public Sub Main()
      Try
        Dim a as Integer = 10
        Dim b as Integer = 10
        Dim c as Integer
        c = a/(a-b)
      Catch ex as Exception
        Console.WriteLine(ex.Message)
      End Try
    End Sub
  End Module
End Namespace
Imports System

Similar to C#, apart from handling the extensive set of extensions defined by the .NET Framework library, custom exceptions can also be defined by subclassing the Exception class (Listing 3.14).


Listing 3.14 Creating Custom Exceptions (Visual Basic .NET)

Namespace hks
  Module UseCustomExceptions
    Public Sub Main()
      Try
        Dim big_discount as new Discount(56)
      Catch ex as Exception
        Console.WriteLine(ex.Message)
      End Try
    End Sub
  End Module
  Public Class Discount
    Private percent as Integer
    Public Sub New(ByVal percent as Integer)
      Me.percent = percent
      If (percent > 50) Then
        Throw New TooBigDiscountException("Discount > 50%")
      End If
    End Sub
  End Class
  Public Class TooBigDiscountException
    Inherits Exception
    Public Sub New(ByVal msg as String)
      MyBase.New(msg)
    End Sub
  End Class
End Namespace

Delegates

New to Visual Basic .NET is the capability of using delegates or function pointers (Listing 3.15).

Listing 3.15 Using Delegates (Visual Basic .NET)

Imports System
Namespace hks
  Module Use Delegates
    Delegate Sub MyDelegate(ByVal msg as String)
    Public Sub Main()
      Dim msg As String = "Hello Delegates"
      Dim d1 as MyDelegate = AddressOf PrintOnce
      Dim d2 as MyDelegate = AddressOf PrintTwice
      d1(msg)
      d2(msg)
    End Sub
    Public Sub PrintOnce(ByVal msg as String)
      Console.WriteLine(msg)
    End Sub
    Public Sub PrintTwice(ByVal msg as String)
      Console.WriteLine("1." & msg)
      Console.WriteLine("2." & msg)
    End Sub
  End Module
End Namespace

Events

Visual Basic developers have traditionally enjoyed the benefits of an easy-to-use event-handling system (Listing 3.16).

Listing 3.16 Using Events (Visual Basic .NET)

Imports System
Namespace hks
  Module Events
    Friend WithEvents button As Button
    Public Sub Main()
      button = New Button()
      button.Click
    End Sub
    Public Sub Button_OnClick Handles button.OnClick
      Console.WriteLine("Button Clicked")
    End Sub
  End Module
  Public Class Button
    Public Event OnClick
    Public Sub Click()
      RaiseEvent OnClick()
    End Sub
  End Class
End Namespace
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020